Question
Hi, Tom,
There are no experts listed under greenhouse, so I decided to try the guy with experience.
Just built my 10X20' greenhouse with all sliding glass patio door walls, 6mm uv ceiling and 6mm uv roof, all double glazed.
my seeds have germinated fantastically.  The inside temp. can rise quite quickly to 95degrees F.  I have seeded broad spectrum from cool loving lettuces and spinach to hot loving peppers and tomatoes.
I live in a remote area and generate my own electricity from micro-hydro and have therefore an unlimited source of free power and a fan/elect 220V heater for all year growing.
What should be the max and min temperatures that I should strive for?
I am a bit of a recluse and just got the internet by satellite last month and cannot afford really high tech solutions.
thank you
Fred

Answer
Hi Fred,
Thanx for your question.  I wouldn't let my greenhouse get higher than 90 degrees.  You know your lettuce and other cool loving veggies won't like this.  Now Fred, it depends on what you want to do.

To grow tomatoes, peppers, eggplants from seed.  Start them warm 75 degrees and once they germinate keep them cool around 65 degrees.  You start these plants in December or January so that you can get your temps down if you need to.  Most perennial flowers that are hardy to zones 3-8 germinate at 75 degrees but need to be cooled down to 60-65 once they germinate.

Shade loving plants will not like higher temperatures.  Oh, by the way, the spinach will bolt (go to flower and become tough and bad tasting) if it stays over 65 degrees in your greenhouse.  Now, there are some fans you buy for a green house that will help you keep the temperatures cooler.  Charley's has a wide selection.  Do a Google search for "greenhouse supplies"  (Google.com) and you'll see vents that are activated by heat.  I don't recommend growing spinach, peas and other cool weather veggies in the green house.  Unless you're doing it in the dead of winter because it just gets too warm.  Don't let the temps go below 40 degrees though.  If you have heat loving plants don't let the temps go below 55 degrees.  Tomatoes and peppers will stop setting fruit below 55 and above 90.  I hope this helps.
Tom